The chemical structure of florfenicol is:

Florfenicol is an antibacterial agent that is a structural analog of chloramphenicol and thiamphenicol. Florfenicol, however, unlike chloramphenicol and thiamphenicol, has a fluorine atom instead of a hydroxyl group at the C-3 position of the core structure. Bacterial resistance to chloramphenicol and thiamphenicol is usually attributed to acetylation of the 3′ hydroxyl group by the action of chloramphenicol acetyl transferase. Since florfenicol does not possess the 3′ hydroxyl group, such a mechanism of inactivation is not possible with florfenicol, thus making florfenicol a highly useful antibiotic.
Florfenicol is active against a variety of microorganisms including Citrobacter, Proteus mirabilis, Proteus sp., Shigella, Salmonella, Providencia, Bacteroides, Staphylococcos aureus, Enterococci, Pasteurlla haemolytica, Pasteurella multocida, Haemophilus somnus, and Haemophilus influenza. Conversely, Serratia marcescens, Pseudomonas aeruginosa, and Acinetobacter, have been found to be resistant to florfenicol. Literature suggests that typical minimum inhibitory concentrations (“MICs”) of florfenicol for various bacteria range from 0.3-1 μg/mL.
Dosage schedules for antibiotics are designed to maintain serum or tissue levels above the MIC for the target organism for a period of time sufficient to clear the infection. Drugs that are cleared rapidly must be administered in multiple doses to maintain effective levels. For example, the commercially available florfenicol composition, NUFLOR™, when used to treat a bacterial infection in cattle, is indicated for administration by intramuscular injection on day 0 followed by a second administration on day 2. Such multiple dosing is inconvenient.
US published application no. 2005/0041428 discloses esters of florfenicol, wherein the hydroxyl group has been esterified. The published application discloses that the esters, when administered to cattle, provide a florfenicol level in the blood serum of the animal that has a different T1/2 and Cmax compared to florfenicol.
EP 0 014 437 discloses a large genus of compounds that encompasses florfenicol and alkyl esters of florfenicol.
There remains a need in the art, however, for compounds that, when administered to an animal, provide a therapeutically effective level of florfenicol in the blood serum of the animal for a sufficiently long period of time to avoid having to be administered multiple times to treat an infection and, in particular, to avoid administration by multiple injections. Multiple administration is inconvenient. The present invention addresses this need as well as other needs in the art.